As a synthetic route for a hydrogen-containing 2,2-difluoropropane, a method has been known wherein trichloromethane or the like is added to an ethylene having a difluoromethylene unit, such as 1,1-dichloro-2,2-difluoroethylene in the presence of aluminum chloride. However, by this method, not only the desired product but also a by-product which has a methylene group other than 2,2-difluoroethylene and which has a boiling point close to that of the desired product, is likely to be formed. Thus, it has a drawback that in order to obtain a product with a high purity, a multi-stage purification process is required.